Developing Physics-Based Virtual Simulation Technology for Natural Orifice Translumenal Endoscopic Surgery (NOTES) NOTES is an emerging revolutionary surgical paradigm, being viewed as a natural successor of laparoscopic surgery, where internal organs are accessed by perforating the viscera (stomach, colon or vagina) using a flexible endoscope inserted through natural orifices such as the mouth, anus or vagina; without making any incisions on the surface of the body. Such scarless procedures would not only lead to better cosmetic results but also enhance the prospects of decreased wound infections and incisional hernia, as well as operative stress, postoperative immobility and pain. However, animal studies have shown serious interoperative difficulties as well as post operative complications. Hence, the current enthusiasm regarding NOTES should not overtake a cautioned approach to the implementation of this new technique. Before NOTES can be safely introduced to humans in the United States several fundamental barriers to its development must be overcome including (1) discovering optimal techniques for accessing the intra-abdominal organs; (2) ensuring that the pressure inside the abdomen does not rise to dangerous levels or there is no leakage into the GI tract when gas (air or CO2) is pumped into the body cavity (this is known as pneumoperitoneum and is achieved through a process known as insufflation) through the endoscope to increase work volume; (3) maintaining spatial orientation inside the body cavity; (4) achieving near perfect closure of the puncture site in the gastric wall (gastrotomy closure); (5) prevention of infection; (6) control of intra-peritoneal hemorrhage; (7) developing novel instrumentation and (8) novel training regimens. The current paradigm is based on testing porcine models which is time consuming, resource intensive and severely delimits the number of possible alternatives that can be tested. To vastly accelerate the development of NOTES procedures and devices, we propose to develop the first virtual reality (VR)-based NOTES simulator with both visual and haptic (touch) feedback. While VR-based simulators exist for both laparoscopic surgery and gastrointestinal endoscopy, none exists for NOTES. Existing technology is inadequate for NOTES simulation and major technological hurdles - not encountered in GI endoscopy or laparoscopic surgery - must be overcome. The most significant of these hurdles include (1) realistic modeling of multilayered hollow organs (e.g., esophagus, stomach, intestines, rectum and vagina) based on physical experiments; (2) simulation of the interaction of flexible surgical tools with soft tissues; (3) physics-based techniques of ensuring the effectiveness of pneumoperitoneum and the integrity of gastrotomy closure and (4) developing realistic interfaces. The aim of the present proposal is to overcome these preliminary challenges and develop the first VR-NOTES simulator which is firmly based on physical experiments and surgical experience and is responsive to physiological consequence of surgical complications. The simulator must undergo extensive validation before it can be used in a clinical setting. A multidisciplinary team with collective expertise in physics-based medical simulation, biomechanical organ modeling, human factors engineering, interventional gastroenterology, laparoscopic and gynecologic surgery has been assembled to achieve the following specific aims in a 4-year R01 research project: SA1) To combine the latest 3D anatomical models with physics-based tissue deformation models to simulate the interaction of flexible surgical tools with detailed deformable organ models that occur in NOTES procedures; SA2) To integrate the computational models and experimental data generated in SA1 and develop the prototype of a virtual NOTES appendectomy (appendix removal) simulator which incorporates physiological consequence of surgical complications and allows comparison of alternate surgical procedures and devices; and SA3) To establish the validity of the computational models and the VR-NOTES simulator developed in SA2.